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How to Enable Direct Memory Access (DMA)
Article ID: 258757 - View products that this article applies to.
This article was previously published under Q258757
This article describes how to enable Direct Memory Access (DMA) on your Windows 98-based, Windows 95-based or Windows Millennium Edition-based computer. DMA (also referred to as bus mastering) is a technique that some components and devices use to transfer data directly to and from memory without passing through the Central Processing Unit (CPU). DMA reduces CPU overhead by providing a mechanism for data transfers that do not require monitoring by the CPU. The number associated with DMA indicates the direct memory access channel that the component or device uses to transfer data to and from memory. The following topics are included in this article:
Determine if DMA Is Enabled on Your ComputerBy default, DMA is enabled for hard disks on Windows 98-based and Windows Millennium Edition-based computers, but it is enabled only with some specific versions of Windows 95 that are listed below. First, determine if DMA is enabled on your computer.
NOTE: If DMA is already enabled, you do not have to perform any of the following steps.
For additional information about how to determine if DMA is enabled on your computer, click the article number below to view the article in the Microsoft Knowledge Base:
141497DMA support for Windows 95 is available in Original Equipment Manufacturer (OEM) versions of Windows 95. If you purchased Windows 95 (the full or upgrade version) from a retail store, you have a retail version of Windows 95. Retail versions of Windows 95 cannot be upgraded to OEM versions, and there is no separate download to enable DMA support in retail versions of Windows 95. If you have an OEM version of Windows 95 that does not have DMA support, contact your OEM.
(http://support.microsoft.com/kb/141497/EN-US/ )How to Use Device Manager to Check the Status of a Resource
To determine the version of Windows 95 you are running:
OEM Version IdentificationWindows 95 may have been preinstalled on your computer. These installations are referred to as OEM installations. An OEM Service Release (for example, OSR2) is an updated version of a product for personal computer manufacturers (OEMs) to preinstall on new personal computers. This allows OEMs to install an integrated Windows 95 product that contains the latest available individual updates and supports recent advances in hardware that require core operating system support.
Additional OEM Information
How to Enable DMA for a Hard DiskIf you are using Windows 98, Windows Millennium Edition (Me) or a version of Windows 95 that includes DMA support, DMA is already enabled for your hard disk by default. If your version of Windows 95 does not include DMA support, use either of the following methods:
Method 1Obtain and install the most current driver for your motherboard that provides DMA support. For information about how to do this, consult the motherboard manufacturer, or view the documentation included with your motherboard or computer.
Method 2You can install any version of Windows 98 or Windows Me to obtain support for DMA.
How to Enable DMA for a CD-ROMTo enable DMA for a CD-ROM: